Tridirectional actuator

ABSTRACT

The device is a portion of a missile control system used to generate the forces to change missile attitude. A three channel fluid amplifier with its exits located at 120* intervals around the missile body in a plane orthogonal to the long axis is the motive device. It is controlled by a single, electrically driven port venting mechanism, which is energized by an electronically generated sequence of pulses. These switching pulses are formed to produce a proper force time product in the pitch and yaw planes without cross coupling.

ilnite tates Leonard [73] Assignee: The United States of America asrepresented by the Secretary of the Army [22] Filed: Aug. 4, 1971 [21]Appl.No.: 168,882

[75] Inventor:

[52] US. Cl. ..244/3.22, 60/229, 239/265.23 [51] Int. Cl. ..F41g 7/00,B63h 25/46 [58] Field of Search ..244/3.l5, 3.20, 3.21,

[56] References Cited [451 Apr. 10,1973

3,278,140 10/1966 Evans ..244/3.22 2,974,594 3/1961 Boehm ..60/229XPrimary Examiner-Benjamin A. Borchelt Assistant ExaminerJames M. HanleyAttomeyl-Iarry' M. Saragovitz et al.

[5 7] ABSTRACT The device is a portion of a missile control system usedto generate the forces to change missile attitude. A three channel fluidamplifier with its exits located at 120 intervals around the missilebody in a plane orthogonal to the long axis is themotive device. It iscontrolled by a single, electrically driven port venting mechanism,which is energized by an electronically generated sequence of pulses.These switching pulses are formed to produce a proper force time productin UNITED STATES PATENTS the pitch and yaw planes without crosscoupling.

3,273,801 9/1966 Wilhite ..239/2 65.23 2 Ciaims, 7 Drawing ON TIME i ONTIME IN UNITS IN UNITS 2 2 NOZZLE n NOZZLE I NOZZLE '1 NOZZLE I! 8: HI

NOZZLE III +1 -I O l O PITCH COMMAND- Bcp YAW COMMAND- Boy PATENTED APR1 01975 SHEET 1 [IF 3 John P. Leonard,

INVENTOR- PATENTEI] APR 1 0 I973 SHEET 2 [IF 3 FIG.4

FIG.3

m I M E H L M F. H N L n m m m mN TU N W u 3 2 I m E H n z a 0 Z N Z O NS W U N 0m 3 FIG. 5

John P. Leonard,

INVENTOR.

PATENIEB 1 01m 3 726.496

SHEET 3 [IF 3 INPUT TO M|$$|LE ON TIME SEQUENCE VENT CONTROL PLANEMECHANISM CONTROLLED (STANDARD UNITSI m P |.5 Bcp I 0 Y I n P I- 5 Bcp HI Y H Bcy I O P l+ Bcp m Y |Bcy FIG. 6

I 111 RI (-5 BCP) Q--W b .I -Ie-- GAIN-I 1 11,11 I (Bcy-.5 Bop) c .v. A(II-I I (2) I/ I d I I I 9 '-'wv' /C| I I m 'Eref I I CgMPARIIPR B J &Eref SEQUENCER i I m (a) D r C FIG. 7 1:

INHIBIT Ife John P. Leonard,

INVENTOR. 522' BY W 7,

TRIDIRECTIONAI. ACTUATOR BACKGROUND OF THE INVENTION One of theobstacles to the attainment of cheap missiles is the inherent cost ofthe mechanism which are required to generate the forces for control ofthe missiles flight path. These mechanisms which, as a general categorycan be called actuators, normally are used in combinations of two,three, or four devices for a single missile. The device described hereinattacks the cost problem in two ways: first, a low cost fluidicmechanism is utilized to control the flow of gases; second, only onesuch mechanism is required to control the missile in both pitch and yawplanes. The basic flow control mechanism can be used to control flows ofbottled gases 'as a direct reaction jet system or injectants to operateas a secondary injection mechanism.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic representationof the rear end of a missile showing the main nozzle and the manner inwhich the subject invention is incorporated therein.

FIG. 2 is a schematic section of the rear end of a missile taken on 2-2of FIG. I and illustrates the directional forces applied by the gas flowfrom the present invention.

FIG. 3 is a schematic representation of the tridirectional fluidicmechanism.

FIG. 4 is a schematic representation of the vent control valve assemblyused in conjunction with the tridirectional fluidic mechanism ofthesubject invention.

FIG. 5 is a graphic representation of the distribution of on timeintervals for the pitch and yaw channels.

FIG. 6 is a tabular representation of the on time intervals and theelectrical control for the vent valve mechanism.

FIG. 7 is a schematic representation of the electrical circuitsassociated with the controls for the vent valve assembly.

DETAILED DESCRIPTION OF THE INVENTION Referring now to the drawings, andparticularly FIG. 1, wherein, 10 generally indicates the rear portion ofa missile incorporating the invention. The missile portion showncomprises the missile skin 12 and an exhaust nozzle 13. Between thenozzle 13 and the missile skin 12 is a fluidic control mechanism 14 anda vent control mechanism 16 therefor. The fluidic control mechanism 14is provided with an inlet duct 18 communicating either with the highpressure gas in the motor chamber 20 of the missile as with a gas bottlenot shown. Three outlet ports from the fluidic control mechanism )14 areconnected by ducts 22, 24 and 26 respectively, to three outlet ports I,II and III located in the missile skin 12 adjacent the rear end of themissile at points spaced 120 around the periphery thereof as illustratedin FIG. 2.

Turning now 'to FIGS. 3 and 4,- the fluidic control mechanism 14comprises a housing 30 having a chamber 32 formed therein. The chamber32 is connected on one side to inlet duct 18 and on the other side tooutlet ducts 22, 24 and 26. Two vent ports 34 and 36 control the flow offluid through the chamber 32 to selectively direct flow to the outletducts 22, 24 and 26.

Bcp), Bcp and Bcy are formed and stored.

The vent control mechanism 16 comprises a flapper valve 40 pivotallymounted at 42 at a point midway between ports 34 and 36 whereby rockingmotion of the flapper valve may selectively close one or the other ofthe vent ports 34 and 36. Two plungers 44 and 46 are connected adjacentthe opposite ends of flapper valve 40 and extend into a solenoid coilmechanism 48. Application of a positive voltage will cause the flappervalve 40 to rock in one direction to close one vent port, while anegative voltage applied will cause the flapper valve 40 to rock in theopposite direction to close the other vent port. A neutral, or zerovoltage, allows both vent ports to remain open.

The control force and time integral achieved with this mechanism islinearly variable in the positive and negative directions over astandard switching sequence in response to two electrical commands Bcpand Boy, which are respectively the commanded force time integral in themissile pitch direction and the commanded force and time integral in themissile yaw direction. The mechanism responds independently to each ofthese command signals.

A standard switching sequence consists of six standard time units. Threeof these units are assigned for control in the pitch direction and threein the yaw direction. In response to any value of Bcp or Bcy, the fullthree units of on time are used, but the distribution of on time betweenexhaust channels is adjusted such that the vector sum of thrust-on-timeproduct lies in the desired control plane, and is linearly proportionalin magnitude to the command in that plane.

FIG. 5 represents the on time for each exhaust as a function of Bcp andBay. A standard switching sequence occurs in the order III, I, II, II,I, III. With zero inputs, i.e., Bcp 0, Bcy 0, the exhaust flows dwellsfor one time unit in each position in the sequence. Note that eachposition occurs twice in the sequence, and further, that it can beconsidered to consist of two sequences interleaved, namely, III, II, Iand I, II, III. The firstsequence is assigned to control of the pitchplane,

while the second is assigned to yaw. The distribution of dwell times ineach part of the sequence is in accord with FIG. 5 and FIG. 6.

The switching logic required to sequence the actuator is readilyachievable, using circuits composed of relays and operationalamplifiers. The critical portion of a mechanization .with electroniccomponents is presented in FIG. 7. This figure is organized to illus--trate function only. The circuit must be modified for actual componentsused. It is also possible to mechanize a device using fluidic elementsif Bcp and Bcy are fluidic rather than electrical signals.

The electronic mechanization functions as follows: Immediately prior toinitiation of a standard sequence, i.e., closure of contact a, thesignals Bcp and Hey are sampled. The circuit to achieve this function isnot shown. Voltages proportional to 0.5 Bcp, (Bcy 0.5

Starting from the right of FIG. 7 and workin towards the left, when acurrent I flows into coil C, the voltage state of the output of D, (3)is changed from its initial value to a subsequent value in the sequence0, O, Only one change occurs for each current surge through the coil. Aninhibit circuit prevents a change of state on (3) if relay C is closed.In addition,

each time a current flow occurs, the capacitor around A is momentarilyshorted by RI, and the input contacts are sequenced, i.e., the closedcontact is opened and the next in the sequence closed in the order a, b,c, d, e, a, b, 0, etc. Contact CI is closed whenever c is closed.

Comparator B compares the voltage output of integrator A on line (1)with a reference voltage E reference. When voltage at (1) is positiveand exceeds E reference in magnitude, a current is delivered to coil 1.If contact C1 is closed, the voltage at (1) must exceed 2 times Ereference.

In the absence of an input signal, (E reference)/t, will be integratedand achieve voltage output adequate to trip the comparator in A tseconds. In the presence of a signal, integration time to achieve tripvoltage will be linearly increased by a positive input signal anddecreased by a negative one. The state of switches a through e,determine which signal modulates the time between switching and thuscontrols the time that 0, or voltage is issued from the sequencer at D.The state of this voltage determines the state of the vent controlmechanism, which, in turn, controls the channel through which fluidexhausts from the actuator.

The logic for the tridirectional actuator is as follows:

1. Flow must be switched from exhaust III to I and thence to II. Flowmay not be switched directlyfrom-II to Ill or III to II. Thisrestriction is imposed by the fluidic mechanism. This does not precludea zero or almost zero dwell time in any position.

2. If a cycle time of six units duration is allocated to complete onecontrol cycle in pitch and yaw, then for any Bcp or Bcy three units oftime must be used for control of either pitch or yaw plane. No more orless.

3. A standard sequence of states will be assumed such that flow isswitched from exhaust III to exhaust I to exhaust II to exhaust I toexhaust III. Dwell times in each position will be divided such that thesequence III, I, II, II, I, III will be divided into two sub sequencesIII, II, I and I, II, III. Dwell time in the first sub sequence will bedetermined by a pitch plane command, and no force time product will becontributed to the yaw control plane. Dwell time in the second subsequence will be determined by the yaw command, and no force timeproduct will be contributed to the pitch control plane.

It should be noted that this restriction eliminates coupling of theplanes in a non rolling missile.

Consider the following signal inputs:

a. Bcp 0. Exhaust channels III, II and I are each on for one unit oftime. (3 units of time total) Force time product, pitch =1 +'(0.5) (O.5)0

Force time product, yaw 0.707 0.707 O b. Bcp 1. Exhaust III on 0.5 unitsof time, II on 0.5, Ion 2. (3 units of time total) Force time product,pitch 0.5 (O.5) 0.5 (0.5)

Force time product, yaw 0.5 (-O.707) 0.5

0. Bcp 1. Exhaust III on L5 units of time, II on 1.5, I on 0. (3 unitsof time total) Force time product, pitch 0.5 1.5) O.5

Force time product, yaw 0.707 1.5) 0.707

Using similar procedures to examine yaw, it can be shown that yaw inputcommands will contribute no energy to the pitch plane and will alsoconsume three units of time each.

It should be noted that there is a slight gain difference between thepitch and yaw planes. Normally, this difference can be tolerated;however, in the event it cannot, a slightly longer time unit can be usedfor yaw on time to equalize the gain differences.

It should be noted that while the operation of the device has beendescribed in connection with laterally directed jet orifices I, II andIII spaced at about the periphery of the rear end of the missile wherebythe gas exhausting from the several orifices will provide a directthrust to move the rear portion of the missile to realign its directionof travel, the same principles are applicable and the invention isequally applicable to a structure wherein the orifices I, II and III arelocated in the main thrust nozzle to provide secondary injection intothe exhaust stream from the motor to change the direction of main jetthrust thus achieving the same realignment of missile direction.

ICLAIM: j

1. A missile attitude control system comprising:

a tridirectional fluid amplifier having an inlet and three outlets;

means for supplying high pressure fluid to the inlet of conduit meansconnecting said outlets from said fluid amplifier to three exhaust portslocated 120 apart around the periphery of said missile adjacent the rearend thereof, the gas eminating from said exhaust ports in a planeorthogonal to the longitudinal axis of said missile;

vent means in said fluid amplifier;

valve means for selectively closing said vent means to direct the gasflow into selected outlets; and

means for controlling said valve means comprising an electronic circuitfor sequencing flow through the three exhaust ports into six timeintervals in equal cycle times, three for controlling pitch and threefor controlling yaw.

2. A missile attitude control system as set forth in claim 1 wherein,said sequencing means includes means for varying the length of the ontime interval for each of the six intervals within a constant cycletime.

1. A missile attitude control system comprising: a tridirectional fluidamplifier having an inlet and three outlets; means for supplying highpressure fluid to the inlet of said fluid amplifier; conduit meansconnecting said outlets from said fluid amplifier to three exhaust portslocated 120* apart around the periphery of said missile adjacent therear end thereof, the gas eminating from said exhaust ports in a planeorthogonal to the longitudinal axis of said missile; vent means in saidfluid amplifier; valve means for selectively closing said vent means todirect the gas flow into selected outlets; and means for controllingsaid valve means comprising an electronic circuit for sequencing flowthrough the three exhaust ports into six time intervals in equal cycletimes, three for controlling pitch and three for controlling yaw.
 2. Amissile attitude control system as set forth in claim 1 wherein, saidsequencing means includes means for varying the length of the on timeinterval for each of the six intervals within a constant cycle time.